Keeping proper tire pressure is a very important aspect of vehicle maintenance. Driving on underinflated or overinflated tires compromises stopping distance, ride and handling, fuel economy, tread wear, and load bearing. Over-inflation decreases traction, causes the tread to wear more quickly in the center, and wear suspension components faster. Underinflated tires have greater flex in the tires' sidewalls. Excessive deflection causes wear closer to the sides, leads to more heat buildup that speeding wear, and greatly reduces fuel economy. Each tire is rated to carry a maximum amount of weight at a prescribed tire pressure. When there is insufficient air pressure in a tire to support a specific load, the extra heat generated in the tire can cause it to fail. Properly inflated pressure during vehicle operation can achieve optimal tire deflection for the best grip and will help to provide even wear and longer life of the expensive tires with substantially improved fuel economy. The concept of a tire inflation system has been implemented on commercial and military vehicles for many years. Many military vehicles are equipped with a central tire inflation system (CTIS) which incorporates both inflation and deflation features, allowing the pressure of the tire to be manually adjusted in response to the road conditions experienced by a vehicle. For example, on relatively soft terrain, the tires could be deflated somewhat to improve traction. In contrast, on harder surfaces, such as paved roads, the tires could be more highly pressurized. Nevertheless, currently available central tire inflation systems do not have real time tire pressure monitor capabilities nor able to intelligently and automatically manage tire pressure with respect to pressure variation, vehicle load and terrain conditions. For commercial vehicles, current tire inflation systems are designed to inflate tire pressure only. Their primary function is to ensure that tire pressure does not fall below a preset tire pressure. Without deflation capability, such systems often can only maintain a preset pressure when the tires were cold but unable to adjust the pressure when the tires got hot and might become overly inflated. Furthermore, one of the most important variables affecting the ideal amount of tire pressure is the load the vehicle tires need to carry but inflation-only system is unable to adjust the tire pressure in accordance to the vehicle load.
U.S. Pat. No. 6,145,559 issued to Rupert Henry Ingram on Nov. 14, 2000 discloses automated tire inflation by using a rotary union to connect a rotary axle and hub assembly. The assembly includes a rotary air connection assembly thread-ably mounted on the hubcap.
U.S. Pat. No. 6,585,019 B1 issued to Anthony L. Ingram on Jul. 1, 2003 discloses a rotary union assembly for use in an automatic tire inflation system for maintaining the desired pressure in the tires on a trailer or other vehicle having pressurized axles. The assembly communicates the valve stems on a pair of adjacent tires with the axle interior through the use of a flexible tube extending between a stationary first fitting thread-ably engaged in the axle spindle and a rotary housing secured against the outside end surface of the hubcap so as to be positioned exteriorly of wheel lubrication compartment and rotatable with the hubcap.
U.S. Patent US 2004/01732296 A1 issued to Jay D. White on Sep. 9, 2004 discloses a tire inflation system include an air supply in selective fluid communication with a tire via a pneumatic conduit. An inflation pressure of the tire is measured with a set-up procedure and the tire is inflated with an extended-pulse procedure.
U.S. Patent US 2006/0018766 A1 issued to Edmund A. Stanczak on Jan. 26, 2006 discloses a tire inflation system includes a hose that connects to a tire via a valve stem. A control valve is in fluid communication with the hose and senses when pressure falls below a predetermined minimum value. When this occurs, the control valve automatically opens to re-supply air to the tire until the predetermined minimum value is achieved.
U.S. Pat. No. 6,144,295 is issued to Brian Adams on Nov. 7, 2000 discloses a central tire inflation system for a work vehicle. The central tire inflation system controls the inflation pressure in the tires of a work vehicle. The central tire inflation system may be placed in an automatic or manual mode. In the automatic mode, the system make changes to the tire pressures according to the tire parameters, terrain conditions, and the operating loads placed on the tire.
U.S. Patent US 2007/0204946 A1 is issued to Martin A. Medley on Sep. 6, 2007 discloses a central tire inflation wheel assembly and valve. The valve includes a main body that is position-able in a sealed and recessed or embedded configuration within the aperture in the wheel rim in communication with the interior of the tire and with a pressurized air source that is used to inflate or deflate the tire.
Typically, these commercial tire inflation systems teach how to inflate air into tires through a rotary union with a one-way check valve that does not have tire deflation functionality. Such system mostly must operate continuously or periodically without knowing current tire pressure in individual tires. When inflation is not activated such systems are unable to detect any flat or leaky tire conditions. While military central tire inflation systems can perform tire pressure inflation and deflation functions, in order to avoid over burning the hub seal, these systems mostly can only check tire pressure during the periodic inflation and deflation activation time. Moreover, these teachings do not address nor provide intelligent tire management solutions to resolve many practical issues, as described below:
(i) Tire Inflation and Deflation with Real Time Monitoring
Properly pressurizing and monitoring tires in real time are utmost important for driving safety and for prolonging the life of tires. However prior commercial tire inflation systems only inflate tires and do not monitor individual tire pressure. It is technically challenging to monitor each tire pressure in real time for tire inflation systems. Currently there are no commercially available tire inflation systems incorporating embedded electronic unit into each wheel valve assembly for monitoring individual tire pressure, and inflate or deflate the tires only when tire pressure is deviate from a predetermined optimal level. Prior teachings generally do not present practical methods to combine real time tire pressure monitor with tire inflation and deflation for commercial vehicle applications.
(ii) Intelligent Tire Pressure Management.
There are many tire inflating systems available on the market and most of them are designed for trailer installation. Such systems mostly use compressed air from the vehicle air tank to inflate tires when tire pressure fell below a preset level. Air from the existing trailer air supply is routed to a control box and then fed into air tubes installed inside each hollowed trailer axle. The air tubes run through the axles to carry air through a rotary union assembly joined at the end of the wheel spindle in order to distribute air to each tire via the valve stem. Generally tire inflation systems do not support intelligent tire pressure management, must inflate the tires continuously or periodically for every trip, and often overly inflate the tires.
Existing tire inflation systems generally use an in-line flow sensor to monitor air flow and do not have direct pressure readings from the tires for controlling the inflation, therefore such systems typically do not know if preset pressure was maintained in the tires. Mostly such systems would deduce that there might be leaky or flat tires if overall pressure was still low after inflating a period of time. This indirect detection of air leak and flat tire is unreliable and usually belated. With frequent system operation, the excessive work load putting on the rotary hub seal unit and the air compressor will wear out the parts sooner and would lead to more expensive vehicle maintenance and even unsafe driving conditions. A tire inflation and deflation system integrated with real tire pressure monitor manages pressure intelligently based on real-time tire pressure data and vehicle load, adjusts tire pressure only when necessary and, as a result, works less and thereby reduces the vehicle maintenance costs. More importantly such an intelligent system improves vehicle safety for it would be able to promptly alert the driver low, leaky or flat tire conditions and enabling the driver to take immediate corrective actions.